The motivation is obvious, as the unmanned aircraft are less expensive and sometimes more effective than other options. They are also less risky. On the other hand, some have questioned the legality and morality of their usage, asking if it is assassination by robot.

Despite the increased attention, little is known about the history of the U.S. military’s investment in drones, which has been going on for decades. It remains to be seen how their use will reshape warfare in the 21st century.

Test your knowledge of drones with our quiz below.

Update: A previous version of this quiz incorrectly stated that the first drone-on-drone fight took place in 2002. In fact, it was a drone against a piloted Iraqi Mig-25 Foxbat aircraft. I apologize for the error!